Process of making soluble yarns and threads of partially carboxymethylated cotton



Patented Nov. 11, 1952 PROCESS OF MAKING SOLUBLE YARNS AND THREADS OF PARTIALLY CARBOXY- METHYLATED COTTON George 0. Daul and John David Reid, New rleans, La.,,assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application April 5, 1950,

' Serial No. 154,202

(Cl. 8-120) (Granted under the act of March 3, 1883, as.

4 Claims.

The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes throughout the world, without the payment to us of any royalty thereon.

This invention relates to yarns and threads and has among its objects theproduction of partially carboxymethylated cotton yarns and threads which disintegrate or are soluble in water and dilute alkaline solutions. Such yarns are useful in applications such as scaffolding fibers for novelty fabrics, knitting of socks together in the string process, etc., where it is desirable to have a yarn which may be removed by washing at some stage in the manufacturing process.

The inventors have previously patented a process of making cotton textiles water-absorbent and rot-resistant by treatment of cotton with monochloroacetic acid and alkali metal hydroxides such as sodium hydroxide, in their patent, U. S. 2,448,153. The products of this patent con tained one carboxymethyl group per from 40 to 5 glucose units. When cottonis carboxymethylated to a greater degree than one group per five glucose units, it swells in water and dilute alkali to such an extent that it either disintegrates or becomes soluble.

Commercially produced carboxymethylcellulose is generally in the form of the sodium salt and has from one carboxymethyl group per two glucoses to one to one substitution and is almost completely soluble in water. However, such materials in no way resemble cotton fibers.

The inventors have previously patented, in U. S. Patent2/l95f767, a process for the preparation of fibers from carboxymethylcellulose by extrusion of a solution of the latter into a metal salt solution, such as aluminum sulphate; Some of .the fibers so produced are soluble in alkaline solutions but these synthetic fibers do not resemble the modified cotton fibers described here.

The inventors have discovered a method of retaining the fibrouscharacter of cotton yarns and threads and most of their tensile strength even though they have been treated severely enough to be soluble in water.

The invention takes advantage of an unexpected discovery that fibers, yarns, or threads, with or without tension, may be carboxymethylated sufficiently to be soluble in dilute alkali, 1% or less, or even in water, yet remain insoluble in the strong alkali needed for the carboxymethylation treatment.

An object of this invention is to produce a water-soluble and dilute alkali-soluble cotton or amendedApfil 30, 1928; 370 0. G. 757) I 2- regenerated cellulose fiber, yarn or thread containing carboxymethyl .substituents in a sufiiciently high ratio to confer water-solubility, preferably at least one carboxymethyl group per three glucose units, by a, method which retains the fibrous characteristics and most of the tensile strength of the fiber.- Another object of this invention is to convert the water-soluble fiber, yarn, or thread to a metal salt which-is insoluble in water but soluble in dilute alkali.

A further object of this invention is to produce a water-soluble, dilute-alkali soluble cotton fiber having carboxymethylsubstituents in the ratio of one carboxymethyl substituent to from one to three glucose units by a method which retains the fibrous character and most of the tensile strength of the cotton fiber.

Other objects are obvious from the detailed disclosure that follows;

Successful carboxymethylation to a greater degree than one group per five glucose units depends mainly upon keeping thewater content of substances which contact the cellulosic-materials, during or after treatment, below 50%. A If the products of this invention should be washed with Water to remove the alkali, they would disintegrate because of swelli'ngand solubility in dilute alkali. However; if most of the excess alkali is removed bycentri fuging, or bysome other mechanicalmeans, and the remainder neutralized with an'acidpreferably acetic, in an aqueous solution of a water miscible organic solvent, such as acetone or alcohol, of concentrations of at least of solvent,.the cotton remains in a useful fibrous form and retains most of its strength. e

By carefully. adjusting the pH, the product may be retained in the form of the sodium salt,

- or if acidified first, may be converted to the ammonium salt with alcoholic-ammonium hydroxidc, or the pyridinium salt with pyridine in alcohol. Other salts may be formed similarly. If V The products formed in the above procedure may be washed or extracted with alcohol orace: tone until free of extraneous materials, then dried. Since the dried materials;.;;are usually somewhat stiffened, it is preferred to apply softening agents in non-aqueous solution such as triethanolamine in alcohol, textile oils; Turkeyzred oil, etc.

Products which are soluble in dilute alkalifmay.

be obtained by a single strong treatment of pref.-

erably kier-boiled and mercerizedcottonx How: I

ever, if greater solubilityis desired, as in water, it is preferred to start withamild treatment, using 7 from 10-30 %;g monochloroacetic acid and 30-40% 'SOdlullIhYdlfOXidE. Potassium-hydroxide has been roundtoworkiinthis reaction; howeverstronger concentrations are required to produce the same results-as with'sodiumhydroxide; It is possible, by increasing the temperature of the reaction with the alkali hydroxide, to expedite the treatmentto a fraction'of a'minute. This causes some strength :loss; however: We prefer; to use room temperature and allow the reaction;to=pro ceed from -30 minutes or lon r. The products of this reactionjmaybe washed in-w-aterand are of, a prior art; When'these products areretreatedwith strong monochloroaicetic'acid,--50%for great-- er concentratiomand sodium hydroxide of 40 to 50% strength, followed by neutralizationin alcohol or acetone, solubilityincreases-t -the point where they disintegrate in'w'ater.

The following examples; which arenot to be considered limiting, exhibit-the "invention-ingreater detail: It isunderstood, in the examples below, that sewing-"thread" and yarn unless otherwise qualified mean cotton sewing thread and cotton yarn. Rayonmeans-regeneratedcellulose.-

Example-I Approximately ten-gr ams of cotton sliver, kierboiled to remove waxes, etc., was soaked in(%- aqueous monochloroacetic acid :containing 0.1% of a wetting agent; (Aerosol OT), .Daddeddo. remove excess, thentreated-with %:sodiumhy, droxide for minutes,.-and washedlwith swat-er). to remove free sodium hydroxide; Substitution was approximately one carboxymethyl group per twenty glucose .units. This .material was re-' treated with monochloroacetic' acid'fo llowed; by 50% sodium hydroxide for one hours It was neutralized with ,5 acetic acid ln a'60%' ethyl'alcohol aqueous solution; ext-ractedireepf alcohol; then made into the ammonium'salt with ammo-- nium hydroxide in "ethyl "alcohol; washed with alcohol, and dried.

The product was still fibrous-and had-a substi-' tion of one carboxymet'hyl group perthree glucose units as determined'bythe copper content of its copper salt. It wassoluble in 1% sodiumhydroxide.

ErampZe'II:

A. 50-yarn skein. of, ,12/5 sewing threadlkierboiled), was-soaked andzpadded with15% mono chloroacetic acid, then soaked in 50% sodiumhy+ droxide for 20 .minutes w-ashed until, free of, excess sodium hydroxide, anddriejd. The carboxy: methyl content was one group per ten glucose 4 units as determined by analysis of the copper salt of the product. The skein was .then padded with 50% monochloroacetic acid and treated with 50% sodium hydroxide for one hour after which it was extracted with 60% aqueous acetone neutralized with 5% aceticacid in 70% aqueous acetone, convertedrto ammonium salt with ammonium hydroxide in acetonathen soaked in a 10% solution of triethanolamine in acetone centrifuged to ab out 50 retention; and dried.

The-dried-product had .a soft hand, retained 72% of its original; tensile strength and was solublein tap water at pH 7.5. It had a substitution of; one carboxymethyl group per 2.5 glucose units.

Example III tion then soaked in50-% sodiumh'ydr'oxide for 20.

minutes, washed'in 95% ethy1 alcohol,- neutralized with 10% acetic acid in 95% 'ethyl alcohol, then converted to theammonium salt withalcoholic ammonium hydroxide and dried.

This yarn retained85-% od:'--i ts tensile strength, elongation increased 25%,:and it had a substituti-on'of vone carboxy-methyl group per three/glucostunits It'was completely soluble-inwater.

Example IV Example V] A skein of 7s/2 ply mercerizedsewing thread of 9 lb. tensile strength'which had been previously treated with 16% mono-chloroacetic acid and 40% sodium hydroxide to obtain a substitution of about. one carb-oxymethyl group per-15 glucose units-was soakedine 50% aqueous solution of mono-chloraceticacid containing 0.1% wetting agent (Aerosol OT). It" was centrifuged to about 50% retentionofyliquidrbased on the weight of the thread.- It was then treated with 50 sodium hydroxide solution-for -30 minutes. The product was squeezed free of excess alkalLwashed in 60% acetone in water, neutralized with 5% acetic acid in 60% aqueous acetone solution, then converted to the ammonium-salt with 5% ammonium hydroxide in 90 aqueous acetone. The dried product had of its original strength and was soluble in water.

e m e A skein' of 50 yardsgof 1100/2 tire-cord type rayon was soaked in'a 50%- solution of monochloroacetic acid in water containing 0.1% of a wetting agent (Aerosol OT). It was then centrifuged to about 50%-pickup and treated with 50% sodium hydroxide solution for 30 minutes. The product was centrifuged free of excess alkali, washed in 95 ethyl alcohol, and converted to the ammonium salt with alcoholic ammonium hydroxide. The product was dried at 50 C. in a blower oven. It was soluble in water and had about 80% of its original strength.

It may be seen from the examples above that cotton or regenerated cellulose fibers, yarns, and threads may be carboxymethylated to an extent greater than one carboxymethyl substituent per five glucose units, yet retain their fibrous character and tensile strength suificient for further textile processing, if the procedures of the invention are carried out.

It is preferred to treat the cotton materials Without tension, thereby allowing greater swelling and penetration of reagents, however, it is possible to treat under tension and obtain similar results.

It is also possible to place the treated sample under tension before drying to increase tensile strength and decrease elongation.

This invention, in one form, is characterized as a process of making water-soluble and dilute alkali-soluble cotton or regenerated cellulose fibers, yarns, and threads containing carboxymethyl substituents in the ratio of more than one carboxymethyl group per five glucose units (sufliciently more to confer water-solubility), but retaining fibrous characteristics and tensile strength, comprising impregnating a material of the group consisting of cotton regenerated cellulose and partially carboxymethylated cotton, with aqueous monochloracetic acid solution having a water content below 50%, centrifuging or squeezing to reduce the aqueous content, treating the impregnated material with alkali metal hydroxide of 45-50% concentration, then on completion of the reaction, reducing the alkali content by extraction with water miscible organic solvent containing not more than 40% water to remove alkali hydroxide or neutralizing with acid in organic solvent and drying. Since a product containing about one carboxymethyl group per five glucose units is the borderline case and is almost, but not quite, soluble in water, our preferred water soluble, fibrous product contains at least one carboxymethyl group per three glucose units, as indicated by the above examples.

Having thus described our invention, we claim:

1. A porcess of producing a water-soluble cellulosic textile, which process comprises: Wetting a cellulosic textile of the group consisting of slivers, yarns, and threads of cotton, regenerated cellulose, and carboxymethylated cellulose containing less than 1 carboxymethyl group per 3 glucose units with aqueous at least 50% monochloracetic acid; mechanically reducing the amount of liquid retained by the so-wetted textile; wetting the resultant partially wet textile with aqueous 40 to 50% alkali metal hydroxide; maintaining the so- Wetted textile for from about 20 to minutes until the textile contains 1 carboxymethyl group per 1 to 3 glucose units; and substantially immediately removing the so-treated carboxymethylated textile from contact with alkali metal hydroxide by a mechanical reduction of the amount of liquid in contact with the textile, and by a neutralization of remaining alkali metal hydroxide with an acid in an aqueous inert water miscible organic solvent having a concentration of at least 60 percent of the organic solvent.

2. The process of claim 1 in which the product resulting therefrom is treated with ammonium hydroxide in an inert organic liquid medium to produce the ammonium salt.

3. The product of the process of claim 1, which is a carboxymethylated cellulose fiber containing one carboxymethyl group per one to three glucose units, which retains the fibrous form and most of the tensile strength of the cellulose fiber but which is soluble in water and in weak alkali solutions.

4. The process in which the product produced by claim 1 is converted into a water-insoluble, dilute alkali soluble carboxymethylated cellulose by soaking said product in a solution of a salt of a metal of the group consisting of copper, iron, silver, mercury, lead, and aluminum.

GEORGE C. DAUL. JOHN DAVID REID.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,236,545 Maxwell et a1 Apr. 1, 1941 2,278,612 Collings et al. Apr. 7, 1942 2,448,153 Reid et a1 Aug. 31, 1948 2,510,355 Waldeck June 6, 1950 2,524,024 Swinehart et al. Sept. 26, 1950 OTHER REFERENCES Textile Research Journal (2) September 1948, pages 551 to 556.

Textile Research Journal, October 1947, pages 554 to 561, Partial Carboxylation of Cotton to Obtain Swellable Fibers, I-Reid and Daul. 

1. A PROCESS OF PRODUCING A WATER-SOLUBLE CELLULOSIC TEXTILE, WHICH PROCESS COMPRISES: WETTING A CELLULOSIC TEXTILE OF THE GROUP CONSISTING OF SILVERS, YARNS, AND THREADS OF COTTON, REGENERATED CELLULOSE, AND CARBOXYMETHYLATED CELLULOSE CONTAINING LESS THAN 1 CARBOXYMETHYL GROUP PER 3 GLUCOSE UNITS WITH AQUEOUS AT LEAST 50% MONOCHLORACETIC ACID; MECHANICALLY REDUCING THE AMOUNT OF LIQUID RETAINED BY THE SO-WETTED TEXTILE; WETTING THE RESULTANT PARTIALLY WET TEXTILE WITH AQUEOUS 40 TO 50% ALKALI METAL HYDROXIDE; MAINTAINING THE SOWETTED TEXTILE FOR FROM ABOUT 20 TO 60 MINUTES UNTIL THE TEXTILE CONTAINS 1 CARBOXYMETHYL GROUP PER 1 TO 3 GLUCOSE UNITS; AND SUBSTANTIALLY IMMEDIATELY REMOVING THE SO-TREATED CARBOXYMETHYLATED TEXTILE FROM CONTACT WITH ALKALI METAL HYDROXIDE BY A MECHANICAL REDUCTION OF THE AMOUNT OF LIQUID IN CONTACT WITH THE TEXTILE, AND BY A NEUTRALIZATION OF REMAINING ALKALI METAL HYDROXIDE WITH AN ACID IN AN AQUEOUS INERT WATER MISCIBLE ORGANIC SOLVENT HAVING A CONCENTRATION OF AT LEAST 60 PERCENT OF THE ORGANIC SOLVENT. 